1. Technical Field
This application relates to techniques for fabricating electronics substrates and semiconductor wafers in general, and more particularly, to systems and methods for removing surplus conductive seed layers from such substrates and wafers using lasers.
2. Related Art
In the Advanced Electronics Packaging and Electronics Substrate processing fields, a so-called “seed layer” of copper (Cu), titanium (Ti), titanium/copper (Ti/Cu), titanium tungsten/copper (TiW/Cu), titanium (Ti), chrome/copper (CrCu), nickel (Ni), palladium (Pd) or the like, is deposited, typically by sputtering or other equivalent methods, onto a wafer or substrate, and then used as a target for plating electrically conductive traces or structures thereon, e.g., bonding pads, redistribution layers (RDLs) and the like. Once the desired conductive traces are formed and the photoresist used for patterning removed, the surplus seed layer, i.e., the seed layer still present on the substrate outside of the conductive traces and structures, must be removed, which is conventionally effected using a wet chemical, dry chemical or a plasma etch process.
However, there are a number of drawbacks associated with these conventional surplus seed layer removal processes. For example, they can prevent the formation of finer pitch structures, they also etch the conductive circuitry that is meant to be left behind, they promote undercutting and thus, yield of the metalized features left behind, leave contaminates on the seed layer that can mask the etch affecting yield, they necessitate increased process times and more expensive methodologies and equipment and thereby constitute an undesirably higher cost of ownership, limited process capability and are less friendly to the environment.
Accordingly, there is a need in this industry for systems and methods for the removal of surplus seed layers that enable higher yields, the production of finer pitch structures and that are simpler, less expensive, and more friendly to the environment than the chemical, dry or plasma etch processes of the prior art.